Syringe devices, such as those adapted to be operably engaged with conventional power injector devices, are designed to provide metered amounts of a particular therapeutic and/or diagnostic compound to a patient via needle and/or other conduit that may be operably engaged with a distal end of the syringe device. Such syringe devices provide a piston assembly that is movable between a distal end of the syringe device and a proximal end of the syringe device. Because the piston assembly is often engaged with an interior sidewall of the syringe reservoir in a substantially air-tight engagement (via one or more wiper seals, for example), the retraction of the piston assembly (by a plunger actuated by the power injector device, for example), towards the proximal end of the syringe assembly may generate a substantial vacuum within the syringe assembly. The generation of a vacuum within a syringe assembly may be caused, for example, when a distal aperture (and/or a conduit downstream of such a distal aperture) defined in the syringe device, is partially or completely occluded (in some cases, by a closed check valve disposed downstream of the distal end of the syringe device).
For example, in some conventional injector devices, a disposable syringe device may be operably engaged with the injector device. The injector device may be capable of automatically retracting the piston assembly to a “replace syringe” position near a proximal end of the syringe device such that the syringe device may be removable from the injector device to facilitate disposal and/or replacement of the disposable syringe device. In some such conventional injector devices, the movement of the piston assembly to the “replace syringe” position causes a plunger of the injector device to disengage from the piston assembly when the piston assembly reaches the proximal end of the syringe assembly. Thus, if a substantial vacuum has been created in the syringe device, the force of the vacuum may rapidly (and sometimes violently) draw the piston assembly towards the distal end of the syringe assembly when the power injector device disengages the piston assembly. The resulting “piston slap” may, in turn, be violent enough to crack and/or shatter a portion of the syringe device. Furthermore, the generation of a negative pressure within the syringe may also be indicative of a retraction of the piston assembly which may, in some cases, cause air to be drawn into the syringe or vapor to form from any liquid content in the syringe. The resulting air bubbles may be hazardous if injected into the bloodstream of a patient via the distal aperture of the syringe. Furthermore, some injector devices may be capable of being operably engaged with multiple syringe devices that may be in fluid communication via a manifold (or a plurality of check valves) leading to a central line leading to a patient. Thus, the generation of a negative pressure in one or more of the syringe devices may be indicative of a commingling of fluids introduced via the syringes. Such commingling may cause cross-contamination and/or compromise the sterility of some reusable components of an injector system. Therefore, for at least the reasons cited herein, it may be technically advantageous to detect a selected level of negative pressure within one or more syringe devices and alert a user of the injector device if and when such a negative pressure is detected.
Some conventional power injector devices include monitoring systems in communication with a controller that drives the plunger assembly for detecting a positive pressure in the syringe during an extension cycle (so as to be capable of delivering a dose of a particular therapeutic and/or diagnostic compound to a patient at a substantially constant flow rate). Furthermore, such conventional systems are configured for monitoring the electrical current in an injector device during the forward or “extension” movement and providing feedback to a control circuit in order to ensure that the dispensing flow rate is relatively constant over the length of the dispensing stroke. However, such conventional systems are not capable of detecting the presence of a selected negative pressure that may be produced during a retraction cycle. Furthermore, such conventional systems are unsuitable for detecting a characteristic a pressure build-up on the “retract” side of a hydraulic actuator (that may be used, for example, in a magnetic resonance imaging (MRI) suite in lieu of an electrically-powered injector), that may be indicative of a negative pressure within a syringe. Thus, conventional injector devices may be incapable of detecting and/or preventing an imminent “piston slap” incident during a retraction cycle in both electrically-powered and hydraulically-powered injector devices. Furthermore, such conventional power injector devices do not include controller logic that may allow for the automatic shutdown of the injector device in cases where a selected negative pressure is detected in a syringe during a retract cycle.
Thus, there exists a need in the art for an injector device that is capable of detecting and quantifying a negative pressure (or vacuum) generated in a conventional syringe device when a distal end of the syringe device is occluded during retraction of the piston assembly within the syringe. There further exists a need in the art for an injector device, method, and computer program product that is capable of correlating at least one of an electrical current drawn by an electrically-powered actuator and a hydraulic pressure within a hydraulically-powered actuator, to a negative pressure produced in a syringe during a retraction cycle of the injector device. There further exists a need in the art for an injector device capable of automatically shutting down in response to a detected negative pressure and/or alerting a user of a detected negative pressure produced within a syringe during a retraction cycle. Finally, there exists a need in the art for an injector system that allows for a user to specify a selected negative pressure which, when detected, triggers an automatic shutdown of the injector device and/or the generation of an alert signal that may be perceptible to a user of the device.